The effect of organic isothiocynates on the functional properties of human hemoglobin and erythrocytes will be studied. The structure of the isothiocyanates will be varied to investigate the effect of charge by studying both negatively and positively charged reagents and comparison with the effect of uncharged isothiocyanates. Steric effects in the isothiocyanates will be studied by systematically varying the distance between the charged group and the isothiocyanate moiety. The functional properties to be examined include the effect on the oxygen affinity of the modified protein of the following allosteric effectors: (1) the proton (Bohr Effect), (2) chloride ion, (3) phosphate ion, (4) 2,3-diphosphoglycerate and inositol hexaphosphate. The effect of chemical modification on tetramer-dimer dissociation will be determined to provide insight into the location of the dissociation-linked anion binding sites. Determination of the site of modification will provide valuable structure-function information and lead to the design of chemical reagents that alter the oxygen affinity in a predictable and therapeutically desirable way. Chemical modification that enhances the release of oxygen will find applications in the treatment of acute hypoxia. Chemical modification that stabilizes the oxyconformation has potential in the treatment of sickle cell anemia which is caused by the abnormally low solubility of deoxygenated hemoglobin.